HVAC systems generally receive an air stream and condition the air, which can include changing its temperature and/or humidity, for example. The process invariably consumes energy, and the rate of energy consumption can change all the time due to numerous factors. It is desirable to be able to determine the instantaneous rate of heat exchange, or thermal load, between the air stream and the HVAC system.
Metering the electric power input into the HVAC system is not always feasible, and even when it is, it does not always provide a satisfactory measure of the instantaneous energy dissipation associated with the air itself, especially when the HVAC system has separate components for mechanical control of air flow and for chilling or heating heat exchange elements, or when some of the components are shared across several separate units. At the same time, an accurate determination of instantaneous thermal load can be instrumental in diagnosing waste, improving efficiency and also being able to correctly attribute efficiency gains to their true cause or enabler. A tool that could directly, and reliably, determine the thermal load from the air stream itself, can be a very effective means to diagnose HVAC energy efficiency, identify potential improvements, and confirm the performance and value of such improvements.